What are the Association of Public Safety Communications Official codes known as?

"Association of Public Safety Communications Officials codes", officially known as ten signals, are brevity codes used to represent common phrases in voice communication, particularly by law enforcement and in Citizens Band radio transmissions. The police version of ten-codes is officially known as the "APCO Project 14 Aural Brevity Code".

The codes, developed during 1937–1940 and expanded in 1974 by the "Association of Public-Safety Communications Officials-International" (APCO), allow brevity and standardization of message traffic. They have historically been widely used by law enforcement officers in North America, but – due to the lack of standardization – in 2006, the U.S. federal government recommended they be discontinued in favor of everyday language.

The development of the APCO Ten Signals began in 1937 to reduce use of speech on the radio at a time when police radio channels were limited. Credit for inventing the codes goes to Charles "Charlie" Hopper, communications director for the Illinois State Police, District 10 in Pesotum, Illinois. Hopper had been involved in radio for years and realized there was a need to abbreviate transmissions on State Police bands.

Ten-codes, especially "10-4" (meaning "understood") first reached public recognition in the mid- to late-1950s through the popular television series "Highway Patrol", starring Broderick Crawford.